This invention relates to plastic bags and a method of effecting their self-opening ability. More specifically, this invention relates to plastic bags that are suspended on a releasable hook retaining means and are then efficaciously dispensed.
The self-opening systems described in U.S. Pat. No. 6,171,226 entitled Plastic Bag Bundling System, incorporate methods of releasably bonding together bag mouths, die-cut handles and other related apertures and die-cuts at their die-cut edges or immediately adjacent the cut edges. The bonds at the bag mouth and die-cut handle edges will selectively cause the bags in the bag pack to self-open because the outer surfaces of the front and rear bag walls have a high coefficient of friction and the inside surfaces have a low coefficient of friction. The difference in coefficient of friction may be the result of corona treatment to the outer surfaces, the use of co-extruded films with layers that have a different coefficient of friction, or by applying a weak, diluted adhesive.
When applying the principles as described in U.S. Pat. No. 6,171,226 by using a high coefficient of friction on the outer film layers and lower coefficient of friction on the inside film layers to a bag incorporating the ventilating structure of U.S. Pat. No. 6,113,269, the self-opening of bags may be effected. Since Automatic Ventilating Systems (AVS) are created by a series of cut vent lines, the same bonding action that occurs when die-cutting a bag mouth or handle hole will also occur when die-cutting the vent lines.
Applying AVS is particularly beneficial with bags in which a xe2x80x9cblouse-openxe2x80x9d effect is desirable. This is because the cut lines of the AVS are located below the bag mouth region, in the body of the bag. Thus, when a bag is dispensed from a hookxe2x80x94for instance a handle hookxe2x80x94the bonding at the bag mouth and/or die-cut handle region may initiate the self-opening of the next bag in sequence, but the bonding at the cut vent lines of the AVS below the bag mouth and die-cut handle will tend to cause the bag body to also open wide. The advantage of having a bag that not only has the mouth open, but the body region below the mouth bloused-open, is that it is easier to load. This is particularly true when loading bags on a handle hook dispensing system.
In the process of die-cutting bag stacks to form individual bag tops, die-cut handle apertures, or other mounting apertures, die blade configurations forming the vent lines of AVS are also incorporated. Typically the outer surfaces of the front and rear bag walls have a high coefficient of friction and the inside surfaces have a low coefficient of friction.
As previously described, the film may be co-extruded, corona treated or a form of adhesive is used in order to accomplish the high and low coefficient of friction objectives.
Typically a single die board is used in a single die cutting operation that forms the bag top, handle aperture and AVS vent lines. The die-cutting operation selectively bonds the successive front and rear bag walls together at or adjacent the cut edges of the vent lines, thereby allowing the bags in a bag stack to subsequently self-open when dispensed.